Address review: const ref args, revert lock migration

- TriggerForwarder::operator() now takes const Ts&... to avoid
  copies of non-trivial types (e.g., std::string).
- Revert lock to trigger-based pattern: LockStateForwarder holds
  two pointers (automation + lock), exceeding sizeof(void*) which
  would cause Callback::create to heap-allocate.
- Remove forwarder_extra_args from API since lock was the only user.

esphome/automation.py

@@ -672,7 +672,6 @@ async def build_callback_automation(
     args: TemplateArgsType,
     config: ConfigType,
     forwarder: MockObjClass | None = None,
-    forwarder_extra_args: list | None = None,
 ) -> None:
     """Build an Automation and register it as a callback on the parent.
 
@@ -680,7 +679,9 @@ async def build_callback_automation(
     automation's trigger() directly as a callback on the parent component.
 
     Uses template forwarder structs so the compiler deduplicates the operator()
-    body across all call sites with the same signature.
+    body across all call sites with the same signature. The forwarder must be
+    pointer-sized (single Automation* field) to fit inline in Callback::ctx_
+    and avoid heap allocation.
 
     :param parent: The component object (e.g., button, sensor).
     :param callback_method: Name of the callback method (e.g., "add_on_press_callback").
@@ -688,11 +689,7 @@ async def build_callback_automation(
     :param config: The automation config dict.
     :param forwarder: Optional forwarder type to use instead of the default
         TriggerForwarder<Ts...>. Pass any struct type whose aggregate init takes
-        an Automation pointer as the first field (e.g., TriggerOnTrueForwarder,
-        or a custom component-defined forwarder).
-    :param forwarder_extra_args: Optional list of extra MockObj args to pass to the
-        forwarder after the automation pointer in aggregate init. For example,
-        a lock forwarder needs the lock entity pointer: [lock_var].
+        a single Automation pointer (e.g., TriggerOnTrueForwarder).
     """
     arg_types = [arg[0] for arg in args]
     templ = cg.TemplateArguments(*arg_types)
@@ -708,12 +705,4 @@ async def build_callback_automation(
             if arg_types
             else TriggerForwarder.template()
         )
-    init_args = str(obj)
-    if forwarder_extra_args:
-        extra = ", ".join(str(a) for a in forwarder_extra_args)
-        init_args = f"{init_args}, {extra}"
-    cg.add(
-        getattr(parent, callback_method)(
-            cg.RawExpression(f"{forwarder}{{{init_args}}}")
-        )
-    )
+    cg.add(getattr(parent, callback_method)(cg.RawExpression(f"{forwarder}{{{obj}}}")))

esphome/components/lock/__init__.py

@@ -35,7 +35,6 @@ LockLockTrigger = lock_ns.class_("LockLockTrigger", automation.Trigger.template(
 LockUnlockTrigger = lock_ns.class_("LockUnlockTrigger", automation.Trigger.template())
 
 LockState = lock_ns.enum("LockState")
-LockStateForwarder = lock_ns.class_("LockStateForwarder")
 
 LOCK_STATES = {
     "LOCKED": LockState.LOCK_STATE_LOCKED,
@@ -95,23 +94,11 @@ def lock_schema(
 @setup_entity("lock")
 async def _setup_lock_core(var, config):
     for conf in config.get(CONF_ON_LOCK, []):
-        await automation.build_callback_automation(
-            var,
-            "add_on_state_callback",
-            [],
-            conf,
-            forwarder=LockStateForwarder.template(LockState.LOCK_STATE_LOCKED),
-            forwarder_extra_args=[var],
-        )
+        trigger = cg.new_Pvariable(conf[CONF_TRIGGER_ID], var)
+        await automation.build_automation(trigger, [], conf)
     for conf in config.get(CONF_ON_UNLOCK, []):
-        await automation.build_callback_automation(
-            var,
-            "add_on_state_callback",
-            [],
-            conf,
-            forwarder=LockStateForwarder.template(LockState.LOCK_STATE_UNLOCKED),
-            forwarder_extra_args=[var],
-        )
+        trigger = cg.new_Pvariable(conf[CONF_TRIGGER_ID], var)
+        await automation.build_automation(trigger, [], conf)
 
     if mqtt_id := config.get(CONF_MQTT_ID):
         mqtt_ = cg.new_Pvariable(mqtt_id, var)

esphome/components/lock/automation.h

@@ -66,14 +66,4 @@ template<LockState State> class LockStateTrigger : public Trigger<> {
 using LockLockTrigger = LockStateTrigger<LockState::LOCK_STATE_LOCKED>;
 using LockUnlockTrigger = LockStateTrigger<LockState::LOCK_STATE_UNLOCKED>;
 
-/// Forwarder that triggers an Automation<> when a Lock reaches a specific state.
-template<LockState State> struct LockStateForwarder {
-  Automation<> *automation;
-  Lock *lock;
-  void operator()() const {
-    if (this->lock->state == State)
-      this->automation->trigger();
-  }
-};
-
 }  // namespace esphome::lock

esphome/core/automation.h

@@ -495,7 +495,7 @@ template<typename... Ts> class Automation {
 /// One operator() instantiation per Automation<Ts...> signature, shared across all call sites.
 template<typename... Ts> struct TriggerForwarder {
   Automation<Ts...> *automation;
-  void operator()(Ts... args) const { this->automation->trigger(args...); }
+  void operator()(const Ts &...args) const { this->automation->trigger(args...); }
 };
 
 /// Callback forwarder that triggers an Automation<> only when the bool arg is true.

tests/unit_tests/test_automation.py

@@ -187,7 +187,6 @@ def _build_forwarder(
     automation_name: str,
     args: list[tuple[str, str]],
     forwarder: MockObj | None = None,
-    extra_args: list[str] | None = None,
 ) -> str:
     """Build a trigger forwarder expression the same way build_callback_automation does.
 
@@ -202,10 +201,7 @@ def _build_forwarder(
             cg.TemplateArguments(*arg_types) if arg_types else cg.TemplateArguments()
         )
         forwarder = TriggerForwarder.template(templ)
-    init_args = str(obj)
-    if extra_args:
-        init_args += ", " + ", ".join(extra_args)
-    return f"{forwarder}{{{init_args}}}"
+    return f"{forwarder}{{{obj}}}"
 
 
 def test_trigger_forwarder_no_args() -> None:
@@ -253,10 +249,8 @@ def test_trigger_forwarder_string_arg() -> None:
     assert result == "TriggerForwarder<std::string>{auto_1}"
 
 
-def test_trigger_forwarder_custom_with_extra_args() -> None:
-    """Lock on_lock: custom forwarder with extra args for entity pointer."""
-    lock_forwarder = MockObj("LockStateForwarder<LOCK_STATE_LOCKED>", "")
-    result = _build_forwarder(
-        "auto_1", [], forwarder=lock_forwarder, extra_args=["lock_var"]
-    )
-    assert result == "LockStateForwarder<LOCK_STATE_LOCKED>{auto_1, lock_var}"
+def test_trigger_forwarder_custom_type() -> None:
+    """Custom forwarder type passed directly."""
+    custom = MockObj("MyForwarder", "")
+    result = _build_forwarder("auto_1", [], forwarder=custom)
+    assert result == "MyForwarder{auto_1}"